Workers and websockets

A person's grants and rules are read once and kept on the user object, as Django keeps a person's permissions - so a request asks the database a fixed number of times, however many lists it shows.

A request ends, and the user object with it. A process that outlives a request - a Celery worker, a websocket consumer, a long management command - keeps the user object as long as it likes, and with it what the person held when it was read.

Read the person again

Where access may have changed since, ask about a fresh user object:

user = User.objects.get(pk=user_id)
orders = Order.objects.visible_to(user)

Or forget what is kept, and the next question reads it again:

from clearance.grants import forget_grants

forget_grants(user)

forget_grants forgets the library's grants and Django's permission caches together, so has_perm reads again too.

A task that runs as somebody

Pass the person's key, not the person:

@shared_task
def export_orders(user_id):
    user = User.objects.get(pk=user_id)
    rows = Order.objects.visible_to(user)
    ...

A task queued an hour ago then runs with what the person holds now - a revoked permission is revoked for the task too.